1. Field of the Invention
The present invention relates to hinges for orthopedic braces. In particular, when used in combination with a knee brace, the present lockable hinge provides a locking mode to immobilize the knee joint, and a free range of motion mode for flexing the knee.
2. Description of the Related Art
Many people suffer from various instabilities that compromise their ability to ambulate and/or stand. These instabilities could include musculo-skeletal disorders such as quadriceps deficiencies, or neurological diseases such as muscular dystrophy, multiple sclerosis and polio. These instabilities interfere with the ability of the brain to properly control the muscle groups that are essential for ambulation and/or standing. As another example, people who have suffered strokes or spinal cord injuries also have difficulty controlling these muscle groups. For people who suffer from disorders such as these, walking and standing can be challenging or impossible. Bracing the person's leg so that he or she cannot bend his or her knee helps the person to stand and walk. A variety of leg braces that prevent knee flexion are available.
When sitting or lying down, generally a person is more comfortable if he or she can bend his or her knee. When wearing a knee-immobilizing brace, however, knee flexion is impossible. Thus, a person wearing such a brace must remove the brace whenever he or she sits or lies down. The process of removing the brace is difficult and time consuming. Furthermore, when the person wishes to stand up again, he or she needs to replace the brace on his or her leg. This process is also difficult and time consuming.
A hinge manufactured by Townsend Design and marketed under the name Trigger Lock enables a person to switch between a locked mode and an unlocked mode. In the locked mode, the hinge is freely rotatable between a first flexion angle and a second, maximum, flexion angle. When the hinge reaches a flexion angle less than the first flexion angle, the hinge automatically locks, such that the hinge cannot reach a flexion angle greater than the first flexion angle. By rotating a lever, the person can unlock the hinge so that the hinge can reach a flexion angle greater than the first flexion angle. By rotating a second lever, the person can place the hinge in the unlocked mode. In the unlocked mode the hinge is freely rotatable and does not lock when it reaches a flexion angle less than the first flexion angle.
A hinge manufactured by dj Orthopedics of Vista, Calif., and described in U.S. Pat. Nos. 5,292,303 and 5,409,449 also enables a person to switch between a locked mode and an unlocked mode. The hinge includes a lever that protrudes in a substantially radial direction. A spring biases the lever toward a locked position in which the lever interferes with rotation of the hinge arms. When the lever is in the locked position, the hinge is locked at full extension. The lever is movable to an unlocked position in which the lever does not interfere with rotation of the hinge arms. When the lever is in the unlocked position, the hinge is freely rotatable between full extension and approximately 120° of flexion. A latch secured to an edge of the hinge plates is selectively engageable with the lever to hold the lever in the unlocked position. When the hinge is oriented at any angle short of full extension, and the latch is disengaged from the lever, the lever is biased toward the locked position. However, one of the hinge arms obstructs the lever, preventing the lever from reaching the locked position. When the hinge reaches full extension, the hinge arm no longer obstructs the lever, and the lever snaps into the locked position.
The hinge further includes a flexion-limiting pin and an extension-limiting pin. The pins are selectively engageable with a plurality of apertures on the hinge plates to set ranges of flexion and extension for the hinge. Thus, using the pins a wearer may lock the hinge at full extension by appropriately positioning the pins to prevent flexion.
Another hinge manufactured by dj Orthopedics also enables a person to switch between a locked mode and an unlocked mode. However, the hinge does not lock automatically upon reaching a pre-determined flexion angle. Rather, the hinge includes a two-position switch that is slidable in the anterior/posterior direction. When the switch is in the posterior position, the hinge is freely rotatable between full extension and approximately 120° of flexion. When the hinge is at full extension, the wearer may slide the switch to the anterior position, where the switch locks the hinge at full extension.
Another hinge manufactured by dj Orthopedics, and described in U.S. Pat. No. 5,921,946 also enables a person to switch between a locked mode and an unlocked mode. This hinge also does not lock automatically upon reaching a pre-determined flexion angle. One of the hinge plates includes a locking switch that is slidable toward and away from the other hinge plate. When the switch is slid toward the opposite hinge plate, it engages one of a plurality of slots on the opposite hinge plate, preventing rotation of the hinge. The slots are positioned such that the hinge may be locked at a plurality of different angles of flexion, including full extension. When the switch is slid away from the opposite hinge plate, it disengages the slot and the hinge becomes freely rotatable. The hinge further includes an extension-limiting stop and a flexion-limiting stop. Each stop is slidable between a plurality of positions to set a maximum extension/flexion range for the hinge. In each position, each stop engages a different land on one of the hinge plates to define the extension/flexion limit.